Portugal goalkeeper Rui Patricio had already walked out of the club

Portugal midfielder Joao Mario deflected questions on the crisis engulfing Sporting Lisbon that has seen four national team players at the World Cup rescind their contracts with the troubled club. William Carvalho, Gelson Martins, Bruno Fernandes, as well as Dutch striker Bas Dost, all filed notice with Portuguese authorities on Monday to say they were breaking their contracts with Sporting, claiming "just cause".

Portugal goalkeeper Rui Patricio had already walked out of the club before flying to Russia amid the fallout from last month's horrific gang attack on players and coaches.

"Everything that has to do with questions not related to our national team are not going to be discussed because we are all focused on our games for Portugal and the match with Spain," Mario told reporters at the team's base camp on the outskirts of Moscow.

"It's not a question that should be raised now, we are focused on the game against Spain," added the former Sporting midfielder, who spent the second half of last season on loan at West Ham from Inter Milan.

"Everything that doesn't have to do with the World Cup should be postponed until later."

Several first team players were attacked on May 15 by disgruntled fans wearing balaclavas after they invaded the club's training complex at Alcochete, outside Lisbon.

The supporters broke into the training complex, vandalised the dressing rooms, threatened backroom staff and assaulted players and coaching staff.

In total, 23 fans were arrested and face charges relating to the incident. Mario was keen to steer the attention towards Portugal's opening Group B match against Spain on Friday in Sochi, with the winner in pole position to finish top of a section including Morocco and Iran. "It's always a special moment (playing Spain), we've faced each other many times," said Mario. "Both sides are very well disciplined and both have very experienced players, players who have been around for a long time."

"Portugal and Spain can't be compared on the same level because Spain has a rich football history although we have done well lately too," he added. "We cannot compare ourselves to Brazil or Germany, but we'll do everything we can to go as far as we can."